<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            border: 0;
        }

        .header {
            width: 60%;
            margin: 10px auto;
            list-style-type: none;
            display: flex;
            align-items: center;
            background-color: #28e;
            color: #fff;
            text-align: center;
            border-radius: 2px;
            user-select: none;
        }

        .header>li {
            flex-grow: 1;
            cursor: pointer;
            border-radius: 2px;
            padding: 5px 0;
            position: relative;
        }

        .header>li:hover {
            background-color: #ddd;
            color: black;
        }
        
        .header>li:hover::after {
            border-top: 1px black solid;
            box-sizing: border-box;
            content: "123";
            display: block;
            position: absolute;
            top: 30px;
            width: 12vw;
            height: 100px;
            background-color: #ddd;

        }
    </style>
</head>

<body>
    <ul class="header">
        <li>新闻</li>
        <li>体育</li>
        <li>游戏</li>
        <li>影视</li>
        <li class="home">用户</li>
    </ul>
</body>

</html>